Metal refining



April 12, 1932.

J. O. BETTERTON METAL REFINING Original Filed Jan. 28, 1950 Patented Apr. 12, .1932

UNITED STATE/s PATENT oFElcl-z JESSE O. BETTERTON, F OMAHA, N EBRASXA, ASSIGNOR TO AMERICAN SMELTING AND REFINING COMPANY, 0F NEW YORK, N.. Y., A CORPORATION OF NEW .'J'lilBS'EY METAL REFINING 'Application led January 28, 1930, Serial No. 424,134. Renewed September 3, 1931.

treatment of the impure skimmings and drosses obtained in the process of refining lead` and the selective separation and recovery of certain impurities in said dresses and skimmings such as zinc and bismuth from a 1o lead calcium-zinc-bismuth.dross which may be obtained from the refining of impure lead. A portion of the zinc is recovered as a. commercial product Which may be usedcyclicly 1n the process 0f refining lead and other byproducts are also obtained which may be used in the process cyclicly. y

The invention further consists in the new and novel features of operation and the new and original arrangement and combinations of steps in the process hereinafter described and more particularly set forth in the claims.

Although the novel features which are believe-d to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode ofits operation and the manner of its organization may be better understood by referring to the following description in which a particular commercial embodiment thereof is disclosed. It will be understood however, that the processes and the steps thereof may be modified in various respects without departing from the broad spirit and scope of the invention.

The drawing forming apart of this application is a flow sheet illustrating thepresent process.

In the following description and in the claims the various steps in the process and the details comprising the invention Willbe identified by specificnames for convenience but they are intended to be as generic in their application as the art will permit.

In carrying on the present process a lead dross containing calcium andlzinc with or Without bismuth and other metals is melted under a chloride slag at a sufficiently high temperature to cause the calcium and a portion of the zinc to form a chloride slag which may be removed from the bath, leaving essentially a. lead bath containing zinc and bisi muth. The zinc is largely recovered by h quation and retorted to produce metallic zinc. i The bath is then treated with chlorine gas to remove the remainder of the zinc as a zinc chloride slag and may then be treated in any suitable manner to recover the other metals therefrom.

The invention is particularly applicable to a lead-calcium-bismuth-zinc dross which is obtained in certainprocesses for the refining of lead. It may, however, be applied to various other mixtures for the selective sepa-ration of the above mentioned metals. As a specific example of a manner in which this process may be carried out, a bath of lead bullion containing silver, and vbismuth and other metals is heated to a` temperature of 875 to 900 F., after'which zinc is added While suitably stirring the bath to produce the desired reaction. A zinc-silver dross is formed which is skimmed from the bath.

The bath is maintained at a temperature of 650 F., and a calcium-lead alloy added and stirred into the molten metal. dross comprising a bismuth-calciuni-lead-zinc alloy is removed and treated for the recovery of the zinc contained therein in the manner to be described.- The above method of forming the bismuth dross forms no part of the present invent-ion, but is covered in my copending application, Serial No. 403,920, filed October 3l, 1929, for metal refining. lAfter this dross kis removed chlorine may be added to the bath in sufficient quantities to unite with the calcium and zinc to form slags'ofzincchloride and calcium chloride. The slags may be used for treating the labove mentioned/bismuthA dross as outlined below. To treat the lead-calcium-bismuth-zinc dross for the removal of calciumand zinc it is first melted under'a slag o f calcium chloride and zinc chloride which may beobtained in previous treatment ofthe lead as-above described at a tempera-ture of approximately 1000Q F. Theresulting slag contains substantially all of the calcium content of the bath as calcium chloride and relatively smallamounts of zinc chloride and lead and maybe removed -and A bismuth or owing to the low metal content, it may be wasted if desired.

After the removal of the slag the metal 1s liquated, the liquate portion containing the eater part of thc zinc and thebath containing the greater portion of the bismuth.,y The liquate ymay be heated in retorts for the production of metallic zinc which may be used 1n thcv desilverizing step during the treatment of fresh baiches of lead or sold in the market. A small amount of blue powder is formed in the retorts which may be used in any deslred manner or further treated to remove the zinc therefrom.

The retort metal containing zinc and bismuth is added to the bath which is then treated with chlorine gas to form a zinc chloride slag. This slag contains the -remainder of the zinc and may be added to the zinc chloride, calcium chloride slag with which the bismuth dross is treated. The' bath will contain the remainder of the bismuth and lnay be treated in any suitable manner for' the recovery thereof.

Inb the above process the lead-bismuth-calcium-zinc dross contains approximately 5% by weight of the bullion treated and is so processed as to allow the recovery of a substantial portion yof the zinc as metallic zinc which is in suitable condition for further use in 'desilverization or for the market. The quantity of zinc lchloride slag which is produced in excess of that which can be used for the above described process is reduced to a minimum and the operating time is materially decreased. l

Although certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it'will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and'in its operation may be made by thosev skilled in the art without departing from the spirit of the invention.

What isclaimed is:

1. The process of treating-a lead-calciumbismuth-zinc dross which comprises melting said dross under'a :chloride yslag capable of selectively chloridizing vthe calcium `to form a calcium chloride slag, removing the larger portion of the zinc from the bath by liquation,.removing the remainder of the zinc as a zinc-chloride slag and .utilizing said slag for the removal-of calcium in the step above described. l.

2. The yprocess .of treating calcium-leadbismuth-zinc dross which 4comprises melting said dross under a' chloride'slag capable of selectively chloridizing the calciumwhereby the calcium is removed from the bismuth as a calcium-chloride` slag, removing a portion-of the zinc by liquation and treating said zinc in retort-swhereby metallic zinc is produced.' v Y l 3. The rocess of treatin a mixture containing ismuth-zinc-calclum-lead whlch thebbathA by liquation, treating said portion in retorts to produce blue powder and metallic zinc, returnin the retort metal to the bath, treating sai bath with chlorine gas to remove the remainder of thefzinc as a zincchloride slag and treating the bath to recover the bismuth therefrom.

5. The process of treating a lead-calciumbismuth-zinc dross to remove selectively the calcium and the zinc from the lead and the bismuth, which comprises melting the dross under` a slag of zinc chloride and calcium chloride to ,remove 'the calcium, then concentrating the zinc in a portion of the bath free from calcium and recovering the zinc therefrom as a metal, then adding chlorine to the both in quantities sufficient selectively to remove the zinc as zinc chloride without removing the bismuth or lead.

6. The process of treating lead calciumbismuth-zinc dross to remove selectively the calcium and the zinc from the lead and the bismuth which comprises heating in the presence of zinc chloride to remove selectively calcium and a portion of the zinc as a slag and then treating the residue of the dross with chlorine, to recover the remaining portion of the zinc as zinc chloride for further use cyclically' in said process.

7. The process of treating a mixture of lead, bismuth, calcium and zinc which comprises melting said miXture under a zincchloride, calcium-chloride slag at a telnperature ofy approximately `1000o F. whereby the calcium enters the slag, skimming said slag, separating a portion ofthe zinc from the bath by liquation, treating said portion in retorts to produce blue powder and metallic zinc, returning the retort metal to the bath, treating said bath with chlorine gas to remove the remainder of the "zinc as a zinc- `chloride slag, treating the bath to recover the bismuth therefrom, and returning the zinc-chloride slag to the zinc-chloride, calcium-chloride slag under which the original mixture is melted.

In testimony whereof I have hereunto set myhand. i

' JESSE `O. BETTERTON. 

